And how to convert a +4 output in a -10 signal? I want to connect my mixer balanced monitor out to my speakers amp (rca). My mixer out converts the output in unbalanced if you plug a TS but i think the signal level is the same, +4db.

You could get a di box, some dual compressor limiters can link tr, xlr, +4 and -10 like my behrenger ultragain pro.

You could do the math- something like an 800 ohm dummy resistor pair, or a pair of 1000 ohm potentiometers, bit theres another formula to see how many watts the pots or resistors need to off balance.

You could just always keep the monitor volume send below 1/4.

Forget about all the dB dBv dBu, the short of it is, in the golden radio days, microphones were all unpowered, and around 600 ohms- highly resistant to current, so they were quieter. Instruments had less electrical resistance, 50-100 ohms for an electric guitar or theremin, and were thus louder. The +4 dBv and -10 dBu were ideals- hardly precise standards. So now, every decent mixer has a wide sweeping gain knob, every ( most every) direct box/ preamp has a gain, and daws have normalize features.

A pc and a focusrite solo makes a good drawing board- great for doodling and trying out new ideas, but computers and 1-2 channel interfaces are cheap, anybody can get them- which is great, but they hardly make a full working studio unless you are an unbelievable solo guitarist and dont play nothin else, or u just make really simple music

I think thats to others. U got a mixer- hardware, good. I seriously wouldnt worry about converting +4 to -10, when.you can just pull the monitor sends down to 1/4. But, since u like hardware- do check out the behringer ultragain pro. Ts unbalanced 1/4and xlr balanced ins / outs, and -10/+4 switch for both channels, and limiters!!!